The invention relates to improvements in mechanisms or systems for transmission of torque between coaxial rotary parts. More particularly, the invention relates to improvements in mechanisms which can be utilized for the transmission of torque between coaxial rotary parts at least one of which is movable or should be free to move axially relative to the other part. Examples of structures in which. the torque transmitting mechanism of the present invention can be put to use are so-called continuously variable transmissions (CVT) wherein one of two adjustable pulleys or sheaves can transmit torque to the other pulley or sheave by way of an endless chain or belt. At least one of the pulleys has an axially fixed first flange which is secured to a driving or driven shaft and a second flange which is movable axially of the shaft toward and away from but should share the angular movements of the first flange.
Continuously variable transmissions are becoming increasingly popular for the transmission of torque in the power trains of motor vehicles, e.g., between a manually or automatically operable clutch and a differential for the front or rear wheels of the vehicle. As a rule, a continuously variable transmission (hereinafter called CVT for short) employs a first shaft which is driven by the prime mover (such as an internal combustion engine) in the power train of a motor vehicle and carries a first adjustable pulley, a second shaft which drives the differential and also carries an adjustable pulley, and an endless belt or chain which is trained over the pulleys. Each pulley has a first flange which is affixed to the respective shaft, and a second flange which is movable axially of the respective shaft toward and away from the associated axially fixed flange. The ratio of the CVT is changed by causing or permitting the axially movable flange of one pulley to move axially of the respective shaft toward the other flange of the one pulley simultaneously with a movement of the movable flange of the other pulley away from the axially fixed flange, or vice versa.
Several embodiments of continuously variable transmissions of the just outlined character are disclosed, for example, in commonly owned U.S. Pat. Nos. 5,295,915 (granted Mar. 22, 1994 to Friedmann for xe2x80x9cCONTINUOUSLY VARIABLE SPEED TRANSMISSIONxe2x80x9d), 5,711,730 (granted Jan. 27, 1998 to Friedmann et al. for xe2x80x9cTORQUE MONITORING APPARATUSxe2x80x9d) and 5,725,447 (granted Mar. 10, 1998 to Friedmann et al. for xe2x80x9cPOWER TRAIN WITH INFINITELY VARIABLE RATIO TRANSMISSIONxe2x80x9d).
In a so-called wet-running CVT, the torque transmitting connection between each shaft and the axially movable flange of the respective pulley comprises rotation preventing means of the type employing teeth, splines and/or spheres. On the other hand, a dry-running CVT often employs one or more leaf springs which can yield to permit axial movements of one flange relative to the other flange but are intended to compel both flanges to rotate in the same direction. However, the angular position of the movable flange relative to the angular position of the other flange (i.e., of the flange which is held against axial movement relative to its shaft) varies while the leaf spring or springs permits or permit the axially movable flange to move axially toward or away from the other flange. Such angular displacement entails additional stressing of the endless flexible element, e.g., a chain of the type disclosed in U.S. Pat. No. 4,927,404 granted May 22, 1990 to Rattunde for xe2x80x9cLINK CHAIN FOR AN INFINITELY VARIABLE CONE DRIVE DISK TRANSMISSIONxe2x80x9d or in U.S. Pat. No. 5,427,583 granted Jun. 27, 1995 to Wolf for xe2x80x9cLOW-NOISE, TRIPLE SIDE BAR SPROCKET CHAIN FOR INFINITELY VARIABLE TRANSMISSIONxe2x80x9d.
The disclosure of the commonly owned copending German priority patent application Serial No. 199 53 580.9 (filed Nov. 8, 1999) and the disclosures of all US and foreign patents and patent applications identified in the specification of the present application are incorporated herein by reference.
An object of the present invention is to provide a novel and improved torque transmitting mechanism or system which prevents the axially movable part of an adjustable pulley or the like from turning relative to the axially fixed part during axial movement toward and away from the axially fixed part without the need for the establishment of a direct rotation-preventing connection between the two parts.
Another object of the invention is to provide a torque transmitting mechanism which employs leaf springs or analogous components but in such a way that these components cannot compel the axially movable part to turn (even slightly) relative to the axially fixed part during movement of the axially movable part toward or away from the axially fixed part.
A further object of the invention is to provide a torque transmitting mechanism which is compact, simple and inexpensive but highly reliable for long periods of use, e.g., in the power trains of motor vehicles.
An additional object of the invention is to provide a continuously variable transmission which employs one or more torque transmitting mechanisms or systems of the above outlined character.
Still another object of the invention is to provide a novel and improved torque transmitting connection between a rotary shaft and a part (such as a conical flange of a pulley on the shaft) which should be free or compelled to rotate with the shaft but should be prevented from carrying out any, even slight, angular movements relative to the shaft.
A further object of the invention is to provide a novel and improved method of transmitting torque between coaxial parts one of which must be free to move axially of but must be compelled to invariably rotate with the other part.
Another object of the invention is to provide a novel and improved torque transmitting mechanism or system which employs leaf springs.
An additional object of the invention is to simplify but to simultaneously enhance the reliability of a torque transmitting connection between a driving or driven shaft and an axially movable part which shares all angular movements of the shaft.
Still another object of the invention is to provide a torque transmitting mechanism which can be employed in numerous existing types of dry-running continuously variable transmissions.
A further object of the invention is to provide novel and improved springs for use in mechanisms which serve to transmit torque between a first rotary part and a second rotary part that should be free to move axially of but should not turn relative to the first rotary part.
An additional object of the invention is to prevent excessive stressing of chains which are utilized to transmit torque between the pulleys of a continuously variable transmission.
One feature of the present invention resides in the provision of a mechanism which is designed to transmit torque between first and second members. These members are rotatable about a common axis and at least one thereof is movable relative to the other member in the direction of the common axis. The improved torque transmitting mechanism comprises first and second frames (such as polygonal, oval or circular frames) which spacedly surround the common axis when the mechanism is in use and at least one of which is deformable. The mechanism further comprises a plurality of means (e.g., rivets, threaded fasteners, snap-on fasteners or the like) which serve to secure at least two spaced-apart sections of the first frame for rotation with the first member, a plurality of means (e.g., rivets, threaded fasteners or any other suitable fasteners) for mounting at least two spaced-apart sections of the second frame for rotation with the second member, and a plurality of means (e.g., rivets and/or other suitable fasteners) for non-rotatably coupling the frames to each other at a plurality of locations each of which is disposed between one section of the first frame and one section of the second frame.
The securing means can alternate with the coupling means as seen circumferentially of the common axis when the frame surrounds the common axis, i.e., when the improved mechanism is installed between the two coaxial parts. Each of the aforementioned plurality of locations can alternate with one of the securing means and with one of the mounting means, again as seen in the circumferential direction of the common axis. One of the coaxial members can include a shaft, and the other of the members can constitute a part (such as a conical flange) of a pulley in a continuously variable transmission.
Each securing means can be aligned with one of the mounting means, and the securing means are or can be equdistant from each other as seen circumferentially of the common axis when the frames are mounted in a transmission or the like so that they spacedly surround the common axis of the first and second members. Each coupling means is or can be equidistant from two of the securing means and/or from two of the mounting means.
Each securing means can be spaced apart from the common axis a first radial distance, and each of the mounting means is or can be spaced apart from the common axis a second distance which matches or at least approximates the first distance when the frames are properly mounted in a transmission or the like.
Each frame can include a plurality of braces each of which extends between one of the securing and mounting means on the one hand, and one of the coupling means on the other hand. Each such brace can exhibit a pronounced resistance to tensional stresses and a lesser resistance to certain other stresses, e.g., bending stresses (including torsional stresses).
The improved mechanism can be constructed and assembled in such a way that its first and second frames respectively comprise pluralities of first and second braces. Each first brace can extend between one of the securing means and one of the coupling means, and each second brace can extend between one of the mounting means and one of the coupling means.
At least one of the frames can be made, at least in part, of a suitable metallic sheet material. Such material can be selected with a view to ensure that the respective frame is resilient. The at least one frame can include elongated braces having profiles arranged in a manner to promote resistance of the profiles to compressive stresses. The preferably resilient at least one frame can include weakened portions in the regions of at least some of the securing and/or mounting means.
The coupling means of the improved mechanism are constructed and mounted in such a way that they can move radially or substantially radially of the common axis of the first and second members when the at least one member is caused or permitted to move axially relative to the other member. The coupling means of such mechanism are fixed in the circumferential direction of the first and second members when the mechanism is in use, i.e., when the frames surround the common axis of the two members.
The securing, mounting and/or coupling means can include connections comprising or constituting riveted, threaded, snap-on or snap-in and/or other suitable fasteners which are capable of reliably coupling the frames to each other, of reliably securing the first frame to the first member, and of reliably mounting the second frame on the second member.
Another feature of the present invention resides in the provision of a torque transmitting apparatus which comprises a shaft rotatable about a predetermined axis, an annular member (e.g., a flange forming part of a pulley or sheave) coaxially and rotatably surrounding the shaft and being movable relative to the shaft in the direction of the predetermined axis, and means for transmitting torque between the shaft and the annular member. The torque transmitting means includes first and second frames, a plurality of means for non-rotatably securing the first frame to the shaft, a plurality of means for non-rotatably mounting the second frame on the annular member, and a plurality of means for non-rotatably coupling one of the frames to the other frame. At least one of the frames is deformable in the direction of the predetermined axis.
The coupling means can include fasteners which are equidistant from each other, as seen in the circumferential direction of the annular member, and which are or which can be equidistant from the predetermined axis. Analogously, the mounting means can include fasteners which are equidistant from each other, as seen in the circumferential direction of the annular member, and which are or which can be equidistant from the predetermined axis. Still further, the securing means can include fasteners which are equidistant from each other, as seen in the circumferential direction of the annular member, and which are or which can be equidistant from the predetermined axis.
At least one of the frames can include or can consist of resilient metallic sheet material, such as sheet steel.
Each securing means can be mounted in such a way that it is coaxial with one of the mounting means.
The frames can have identical outlines, e.g., square or other polygonal outlines.
Each frame can include a plurality of identical or different braces each of which extends between one of the coupling means on the one hand, and one of the mounting and securing means on the other hand.
A further feature of the invention resides in the provision of a method of transmitting torque between coaxial first and second rotary members at least one of which is movable in the direction of common axis of such members. The method comprises the steps of securing circumferentially spaced-apart sections of a resilient first frame to the first member so that the thus secured frame spacedly surrounds the common axis of the two members, mounting circumferentially spaced-apart sections of a preferably resilient second frame on the second member adjacent the first frame, and coupling, the two frames to each other at locations which are spaced apart from each other and from those sections of the first and second frames which are secured to and mounted on the respective members. The aforementioned locations are or can be disposed at identical radial distances from the common axis of the two members, and such locations preferably have at least some freedom,of movement radially of the common axis.
The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved torque transmitting apparatus itself, however, both as to its construction and the modes of assembling and utilizing the same, together with numerous additional important and advantageous features and attributes thereof, will be best understood upon perusal of the following detailed description of certain presently preferred specific embodiments with reference to the accompanying drawings.